FLORIDA STATE HORTICULTURAL SOCIETY. 
153 
The expression “cold wave” as a term 
is applied to anti-cyclones of great inten¬ 
sity. Its significance depends on temper¬ 
ature changes within a stipulated period 
over certain divisions of the country. And 
the degree to which the temperature must 
fall in order to verify a cold wave warn¬ 
ing is regularly regulated by the degree 
of cold required to damage crops or other 
interests over sections for which warn¬ 
ings are ordered. 
OLD AND NEW IDEAS. 
There has been sundry hypotheses re¬ 
garding the formation of cold waves. The 
idea was once advanced that the leading 
factor in the formation of the intense cold 
was radiation into space from the upper 
strata of the atmosphere, and a conse¬ 
quent mixing of the upper and lower 
strata. This method was supposed to de¬ 
velop the cold and high pressure. Other 
meteorologists adhered to the belief that 
the cold of winter was simply the descent 
of cold air from above. These theories 
proved untenable, however, for observa¬ 
tions showed that radiation was more 
active in the lower stratum of air. 
Elliott, the meteorologist of India, 
points out that the average daily range of 
temperature is nearly twice as great in 
the plains of India as at the adjacent hill 
stations. This fact has been amply sus¬ 
tained by many of our weather stations, 
those having elevations of five to six 
thousand feet showing higher temperature 
during a cold wave than the lower level 
stations. This supports the accepted be¬ 
lief that cold waves are very shallow. 
Reference has been made by some au¬ 
thorities to the fact that in the formation 
of cold waves the loss of heat by radia¬ 
tion must be very great to overcome that 
resulting from compression. 
4 , 
A GREAT RADIATOR. 
The earth is a great radiator and the 
air rising therefrom experiences reduced 
pressure, expands and becomes cooler. It 
may be stated that many meteorologists 
maintain that the enormous land area of 
the British Northwest Territory, from 
which radiation proceeds the greater por¬ 
tion of the time, is the controlling factor 
in building permanent areas of high pres¬ 
sure, which drift southward as cold waves 
along the eastern slope of the Rocky 
Mountains. The chief features of high 
pressure areas or anti-cyclones are low 
temperature, generally light winds and 
clear, dry weather. The mass of air cir¬ 
culates around a center, the layer of air 
having a movement out from the center 
and the direction of rotation conforms to 
the movement of the hands of a watch 
in this hemisphere. 
Regarding the formation of cold 
waves, General Greely says. “The greater 
part of the anti-cyclones which cause cold 
waves probably ninety percentum are out¬ 
flows of dry air, chilled to a very low tem¬ 
perature by radiation over the barren 
grounds of British America. Without 
doubt, the very low temperature to which 
the air falls is due to the barren treeless 
character of that country, which is cover¬ 
ed by scanty vegetation during summer, 
and free from ice and snow during winter, 
so that radiation from the bare ground 
proceeds with great rapidity during the 
long winter nights in this sub-arctic re¬ 
gion.” 
